Light beam transmission system



FIPSIO R ,100,348

A. Mci. NicoLsoN Nov. 30, 1937.

Examiner UNITED STATES PATENT OFFICE LIGHT BEAM TRANSMISSION SYSTEM Alexander McLean Nicolson, New York, N. Y., as-

signor to Communication Patents, Inc., New York, N. Y., a corporation of Delaware Application April 13, 1934, Serial No. 720,449

plates 30 pushing this result, in one of which Selection is 1 Obtained 0n the basis of theother on the basis of he frequency of Another object of the invention is to transmit a plurality of diierently modulated light beams along a common transmission path and selectively separate said beams at a receiving point.

A further object of the invention is to transmit signals on invisible light beams over common transmission paths and select said beams on the basis of light intensity variations.

A still further object of the invention is to re-transmit signals on light beams in different directions to a plurality of receivers.

It is ralizedthtsmrtrasmission on light beams has been accomplished, the beams being modulated at the transmitter in accordance with a particular signal and reproduced at the receiving station by means of a light sensitive device feeding the proper reproducing device. The present invention, however, contemplates multiplex transmission f l alit of signals om Eon light beam or a light Beam Having a definite 'pa thus accomplishing* multiplex transmission over asystenthat has heretoorebeensuitable for'nly a single channel. The invention cont methods of and means for accomrupti Y l a l employs light lters vhich\ f e rst method l beam for each signal, this monoc omatic light beam being combined with others into a sing beam for transmission over a common pa receiver the different be u o' p ion taking place in the usual manner. Partial reiectors may be inserted along the light path and the signal intercepted and delivered to other receivers. The second method employs electrical oscillators which vary the intensity of a light beam in accordance with the oscillator frequency. Separation is ob` tained at the receiver by electrical lters after the light has been translated into electrical currents. Any type of signal may be transmitted on either system and the systems may be combined. 'I'he invention will be more completely understood by reference to the following detailed description read in conjunction with the accompanying drawing in which:

Fig. 1 is a diagrammatic drawing of a multiiid/produce `a substantially monochromatic lig.)

plex system in which selection is made on the f" nf lightfrequency, a,n.d. .s Y` f Fig. 2 is a diagrammatic drawing of a signalling system in which selection is made on the Referring te Fig. 1 in detaitherert signal sources are shown, these sources being illustrated as a mi hone 5, a radio receiver antenna 6, and itelvipstnsmitter 1, signals f w ch are amplified in rste ampliiers 8, 9, and I0. The outputs of the ampliers are connected to three light producing tubes I3, I4 and I5, respectively. These tubes may be of the crater type and illed with a gas which produces a light dilering from the others. That is, tube I3 may contain hydrogen or neon and provide predominantly blue light, tube I4 may contain mercury or carbon dioxideand provide predominantly green, and tube I5 may contain acetylene and provide predominantly red.` It is also within the scope of this invention to use other modulating means such as a constant intensity light source together with any light 'valve well known in the art. To increase the selection between the colorsand the separation between signals, selective lters Il, I8 and'IS may be employed which will eliminate the undesired light freuencies. The three light beams, (it being understood that other monochromatic beams may be adlied without departing from the invention) may be Joined optically in anywell known manner by the use of prisms such as-22 and 23 and lens 24 cooperating with prisms 25 'and 26. These light beams may be conned and directed in a beam by a lens 2'I, it being understood that the rays may be intermin led or kept alon adjacent paths by the optical adjustment of the prisms and lenses, the light sources being removed from the focus of lens 21 by the use of lenses such as 24.

At the receiver a lens in conjunction with prisms 3l, 32, 33 and 34 and lens 35 separate the light beam into portions or different paths.' The desired monochromatic light is then obtained by passing through lters 31, 38 and 39, 45 where it impinges upon respective photo cells 4I, 42 and 43. These cells may be chosen'according to their light frequency response char- A acteristics. For instance, a @iu/huellggould function to ai d the selectivity of the system in the case gffred lightasodiam or potassium cell would'b morsuitable for blue light, while a rubidium cell would be more sensitive to green light. The outputs of the Ycells may be amplifled in amplifiers 45, 46 and 41. respectively, and 55 basis of the frequency of light intensity varia- 5 v the outputs thereof impressed on any desired positions and impress the different portions on translating device, such as a sound reproducing photosensitlve devices 95 and 9B. These cells are device 48, transmitting device 49, or television connected to filters 91 and 98, respectively, which receiver 50. That is, the microphone 5 is confeed respective amplifiers 99 and |00, the outputs 5 nected with the sound reproducer 48, the televithereof being impressed on the proper receiving 5 sion transmitter 'I with its receiver 50, while the device, such as a sound reproducer IOI and a middle channel may be a re-broadcast circuit. television receiver |02.

To illustrate the light broadcasting principle, In the system of Fig. 2 selection is obtained a partial reflector 55 is shown positioned in the on the basis of frequency of light interruption light beam, the light reflected therefrom being and as this light frequency is translated by the 10 focussed by a lens 56 on a photo cell 51 after photo cells 95 and 95 into electrical currents havselection by a lter 60. The energy from the ing the same frequency, electrical nlters may be cell may be amplied in an amplifier 58 and reused to select the signals by selecting the proper transmitted over antenna 59. It is also obvious frequency. Although two systems have been dethat receivers may replace the antenna 59 and scribed to illustrate the two methods of and apl5 that other reflectors may be positioned in the paratus for the separation on the basis of light light path for utilizing a portion of the transmitfrequency end light interruption frequency, it iS ted energy. to be understood that these two systems may be From the description of the above system, it combined into one so that both methods may be is obvious that selectivity is obtained on the basis Operated Over the same light beam path. Buch 20 of light frequency. The visible light spectrum systems are especially desirable for use by emscontains a plurality of frequencies which when teurs inasmuch as there is no interference with separated into individual frequencies provide difredlc transmission by heterodyning. Such sysferent colors, each color representing substantems are also desirable for secret signalling or for tially a single frequency. These rays are sepa- Signalling Over sllOrt distances Where elerge 25 rately modulated, then mixed with other rays number 0i messages must be confined t0 9 few for transmission over a common transmission channels. path, and then separated by light filters. Beams What is claimed is! of composed light weinig@ 1. A plural channel signaling system compristheir predominant spec ra and signals thereof ing ineens fOr generating e plurality 0f electrieel 30 transmittedand re""ce1ved so as to use en ooncurrents representing individual signals, means centrated energies in corresponding spectra. Alfcr generating light Waves, means for impressing though only three channels have neen illustrated, said electrical currents directly on said last menusing visible light rays, invisible light rays may tiened mee-ns to vary the amplitude 0f seid light $5 also be used as a transmission medium, the inwaves in accordance with the variations in am- 35 visible light forming a channel or channels si- Dlitude 0f Seid currcntS.lr1eenS fcr collecting and multaneously with the visible rays. With invis- Prclectlng Seid light t0 e distant peint ln the ible light rays, of course, it would be necessary to ferm 0f adjacent beams, means at Said distant use appropriate lters, an ultra-violet filter for Point for Separating Seid adjacent light beams 4o ultra-violet light, etc., or corresponding invisinto spatially disposed beamssnd means in each 4o ible refracted light spectra. of said beams for eliminating substantially all Referring now to Fig 2J a Similar system is light frequencies except a certain desired freshown using a microphone signal source 65, and quency a television signal source 66, each of which have 2- A Plural channel signal System in accordrespective amplifiers s1 and se. The output of ence with claim 1 in which seid light waves are 4s the amplifiers feed glow tubes 10 and 1I, these generated by glOW tubes predcmineting in mutubes being of a somewhat different type from tually exclusive frequencies end upon which Seid those in Fig. 1. That is, tubes 1u and 1| are of electrical currents are impressed. and said last the u type which have wound around their mentioned means comprises filters selective of straight sections windings 12 and 13, respectively, the respective frequencies generated by respective 50 these windings being connected to respective ostubcS cillators 14 and 15. oscillators 14 and 15 should 3- A plural channel signalmg system comprisoperate at different frequencies, such as f1 and ing Ineens fOr generating e plurality 0f different fz, these frequencies being relatively high and electrical Signals, Ineens fOr generating light freabove any of the signalling frequencies with quencies, Said means directly i"le-nSleting Suid 55 which they are used, Theupurpose is to vary signals into corresponding variations in light inthe intensity of the light from the tubes at the tenSitleS end distinguishing between Seid signals frequencies of the oscillators. The tubes are 0n the beSlS 0f light frequencies, means for c01- modumted by the incoming sig-nuls being 1m.. lecting said light frequencies into adjacent beams o0 pressed upon the electrodes thereof. The light end for optically projecting said adjacent light 60 from these tubes may be the same and invisible beams t0 9- dstant Point, Ineens et Seid distant Ran, 0r @y Ee alf e1-gj', point fOI spatially dividing Said adjacent light an ble frequencies or a combinationlo'iloth. bca-m5. Ineens at Suid distant point fOr Segregatotli-'types of modulation may 15e" risedin "thisq ine respective frequencies, and means at said dis- 05 system ns in F1g 1, that is, wou known meenamtant point for translating said respective light 65 ou] Shutters, such as perforated disks, may bo frequencies into electrical currents having ampliplaced before a constant light source and the tuile Veflatlcns corresponding t0 the amplitude light impulses modulated by a light valve, variations of said respective light frequencies.

/ The light beams from the tubes are collected 4. A plural channel signalling system comprisby lens 80 and 8l and directed into a substaning means for generating s plurality 0f different 70 tially common path by prisms 82, 83, 84 and 85, electrical Signals, inea-11S fOr translating said sigand then concentrated for projection by a lens nais into corresponding variations in light inten- 89. At the receivers a gathering lens 81 coopersities, said means distinguishing between said ating with prisms 88, 89, 90, 9| and lens 92 and signals on the basis of light frequencies, means 93 separate the beam into diierent portions and for collecting said light frequencies into adja- 75 Examiner cent beams and for optically projecting said arijacent light beams to a distant point, means at said distant point for spatially dividing said adjacent light beams, means at said distant point for sesresating respective frequencies, means at said distant point for translating said respective light frequencies into electrical currents having desired signal without preventing the transmis- 5 sion thereof to said distant point.

ALEXANDER. McLEAN NICOLSON. 

